Instruction for installing gcc 9.3 or gcc 10(experimental) on ubuntu 18.04

	1. sudo apt update
	2. sudo apt upgrade
	3. sudo apt install build-essential
	4. sudo apt install flex
	5. git clone https://github.com/gcc-mirror/gcc.git gcc-10
	6. cd gcc-10
	7. contrib/download_prerequisites    (wait for this command to finish)
	8. cd ..
	9. mkdir build
	10. cd build
	11. ../gcc-10/configure -v --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu --prefix=/usr/local/gcc-10 --enable-checking=release --enable-languages=c,c++,fortran --disable-multilib --program-suffix=-10
	12. make -j 8
	13. sudo make install-strip
	14. Add the following two lines to your shell rc file. For example .zshrc
		export export PATH=/usr/local/gcc-10/bin:$PATH
		export LD_LIBRARY_PATH=/usr/local/gcc-10/lib64:$LD_LIBRARY_PATH
	15. source ~/.<rc file> or logout and login
	16. Compile and run with   g++-10 -std=c++20 ranges.cpp && ./a.out

C++17 & C++20 concepts

	https://www.modernescpp.com/index.php/tag/c-20

C++20 status:

	https://gcc.gnu.org/projects/cxx-status.html or https://clang.llvm.org/cxx_status.html (for clang)